1. Field of the Invention
The present invention is directed to methylene chloride-free, and optionally methanol-free, paint stripper and gasket remover formulations, as alternatives to methylene chloride-based paint strippers and gasket removers.
2. Brief Description of Related Technology
Methylene chloride has been the paint stripper and gasket remover of choice in industry for many years because it removes paints, coatings, and gaskets quickly, and works well on a variety of substrates, including wood and metal. The largest use for methylene chloride in the United States is paint stripping and gasket removal with about 40% of the 360 million pounds sold in the United States in 1994 being for this application.1 Paint stripping and gasket remover products are widely used by maintenance workers at industrial complexes, aircraft painters, furniture makers, and homeowners. Other major uses for methylene chloride include metal cleaning and finishing in electronics manufacturing, and as a process solvent in the pharmaceutical and film coatings industries. Despite the versatility of methylene chloride in a variety of applications, some industry experts believe that the use of methylene chloride in paint stripper and gasket remover products will be curtailed by government regulations due to concern over its toxicity in humans. The U.S. Environmental Protection Agency currently classifies methylene chloride as a Group B2 probable human carcinogen of low carcinogenic hazard.2 
1 Internet site: http://pubs.acs.org/hotartcI/cenear/950925/pg1.html, Aug. 4, 2000, p. 11. 
2 Internet site: http://www.epa.gov/ttnuatw1/hlthef/methylen.html, Aug. 3, 2000, p. 1. 
Accordingly, it would be desirable to replace methylene chloride in such products with a chemical having comparable abilities, while having a less extreme EPA classification.
Other halogenated solvents are known for use in paint stripping and/or gasket removing compositions. For instance, brominated solvents are known, such as n-propyl bromide. n-Propyl bromide is oftentimes recommended as a paint stripper or gasket remover as a cold cleaning solvent or in immersion applications. Another known halogenated solvent is benzotrifluoride (also known as 1-chloro-4-(trifluoromethyl)benzene). See U.S. Pat. No. 5,756,002.
A number of obstacles exist to the successful commercial development of a paint stripper and or gasket remover composition, even one containing a halogenated solvent other than the one carbon variety, such as methylene chloride (or chloroform or carbon tetrachloride). For instance, while a large container of n-propyl bromide might be handy in industrial, large scale operations where the parts to be stripped of paint or from which one or more gaskets to be removed are of significant size, in many instances it is not convenient to perform a dipping operation. Rather, many end users would prefer to be able to apply such a composition directly on the part and remove the unwanted paint or gasket shortly thereafter. However, halogenated solvents, such as n-propyl bromide, themselves are very often low viscosity and thus tend to either run off the part or evaporate quickly after application. This results in incomplete cleaning after one application or the necessity of many repeat applications, with much waste of material and time.
While thickeners may be used to enhance the viscosity of the halogenated solvent, which will improve the run off problem, most conventional thickeners, such as silicas, clays and the like, themselves do not have the proper film forming properties to allow the development of a wet film of the halogenated solvent. In addition, the addition of a thickener will likely create a two part system, requiring agitating mixing prior to application.
There therefore exists a need for formulations for stripping, removing and cleaning parts that are free of methylene chloride, and optionally methanol as well, and provide comparable performance abilities to formulations based on that halogenated solvent.
A methylene chloride-free, single phase, paint stripping and gasket removing composition, comprising a halogened hydrocarbon liquid, having more than one carbon atom; a polar oxygenated organic liquid; and a hydrogen bondable thickener, wherein the polar oxygenated organic liquid and hydrogen bondable thickener are present in sufficent amounts to render the composition in a single phase and to synergistically increase the viscosity of the composition beyond the viscosity of a composition, without either of the polar oxygenated organic liquid or the hydrogen bondable thickener in substantially similar amounts.